EVOLUTION CHARACTERISTICS OF WEAK INTERCALATION IN MASSIVE LAYERED ROCKSLIDES-A CASE STUDY OF JIWEISHAN ROCKSLIDE IN WULONG, CHONGQING

The weak intercalation forms a sliding zone after long-term geological evolution and plays an important role in controlling the stability of massive layered rockslides. In order to determine the formation process of the sliding zone, we take the Jiweishan Landslide as an example and analyze the developmental regularities of the weak intercalation. The weak intercalation can be divided into three stages including the original soft rock, the interlayer shear zone and the sliding zone. In addition, we have comparatively studied the evolutionary characteristics of weak intercalation through the laboratory test of the physical properties, physicochemical properties, and physical mechanics properties. As a result, from the view of the mineral composition, the mean value of the clay mineral content is increased from 4.4% to 16.9%. From the view of the physical properties and the microstructure, the density is decreased from 5% to 6%, and the porosity is increased by 108%. It reflects the decreased density and loose structure due to long-term evolution. From the view of the physicochemical properties, the total content of exchangeable salt is the highest in the original soft rock, followed by the sliding zone, whereas the interlayer shear zone exhibited the lowest value. The organic matter content is gradually increased in the alkalescence evolutionary environment. From the view of the shear creep strength, the internal friction angle is decreased from 57.58°to 29.63°, and the cohesion decreased from 585 kPa to 96 kPa. Based on these data, we analyze the change of the residual sliding thrust of the main section of the Jiweishan Landslide driving block. The residual sliding thrust increases with a decrease in the long-term strength parameter. When the internal friction angle φ < 25° and cohesion c < 129 kPa, the residual sliding thrust of the driving block is greater than zero, and then the driving block is sliding. The conclusions provide an important reference for the study of the development and mechanism of layered rockslides controlled by weak intercalations.